Electric heater



March 20, 1934. F. w., DEARBORN ELECTRIC HEATER Filed June 26, 1933 INVENTOR Patented Mar. 20, 1934 UNITED STATES PATENT OFFICE ELECTRIC HEATER Application June 26, 1933, Serial No. 677,639

1 Claim. (01. 201-67) This invention relates to improvements in electric heating devices.

It is an object of the invention to provide an electric heater which may be readily disassem bled and all parts separated for the purpose of facilitating renewals or repairs, by merely removing a relatively small number of detachable uniting elements.

In the accompanying drawing illustrating the preferred form of the invention,--

Figure 1 is a longitudinal cross-sectional view of the improved heater.

Fig. 2 is a transverse sectional view of the heater, the section being taken along the line 2-2 of Fig. 1.

Fig. 3 is a side view of a guard tube within which other parts of the heater are enclosed, a portion of the tube being cut away to indicate internal structure.

Fig. 4 is a side view of a support of insulating material to serve as a mounting for the heating element, a part of the support being represented in longitudinal cross-section.

Fig. 5 isa cross-sectional view through the support, taken along the line 5-5 of Fig. 4.

Fig. 6 is a longitudinal view of the heating element to be mounted on the support shown in Fig. 4 and enclosed within the guard tube shown in Fig. 3, as illustrated by Fig. 1.

Fig. '1 is a cross-sectional view of a cap to be mounted in and close one end of the guard tube and serve as a mounting for one end of the support.

Fig. 8 is a perspective view of a cap having a portion to be mounted in and close the opposite end of the guard tube and serve as a mounting for the opposite end of the support and as an outlet for the terminals of the heating element.

In Fig. 9 are illustrated cross-sectional views of a pair of uniting elements by means of which the various parts of the heater are held in an assembled relation with the guard tube.

The preferred form of the invention herein disclosed comprises an electric heating element 20 of suitable metal alloy coiled about or otherwise mounted upon a support 21, preferably in the form of atube of insulating material, having its ends mounted in recessed portions of caps 22, 23, also preferably of insulating material, the

coil, support and caps being enclosed within a guard tube 24 preferably of metal.

The annular space between the support 21 and guard tube 24 and between the caps 22 and 23 surrounding the heating element 20, as well as the space within the supporting tube 21, may, if

desired, be filled with insulating material 25, preferably in a finely powdered or comminuted state.

The various parts of the heater thus far described may be held in their assembled relation, as indicated in Fig. 1, by means of uniting elements 26, 27, detachably connected with the guard tube 24. The element 26 may comprise, as indicated, a threaded cap completely closing one end of the guard tube, and the uniting element 27 may comprise a ring having a threaded connection with an end of the guard tube and an annular shoulder 28 extending inwardly over an outwardly-directed portion of the cap 23.

The cap 23 may, as shown, have a portion 29 extended through and beyond the uniting ring 27, and this extended portion may terminate in a part cut away to provide four circumferentially-disposed recesses 30, 31, 32, 33, separated by wall portions 34, 35, 36, 3'2.

Two of the wall portions which are oppositely disposed with respect to each other, as, for example, portions 34 and 36, may serve as supports for binding-posts 38, 39, and a pair of openings 40, 41 may be provided in the cap, the inner ends 30 respectively leading to the interior of the supporting tube 21 and the annular space between the supporting tube and the guard tube, and the opposite ends leading to a pair of recesses in the end of the cap 23, which, as shown, should preferably be oppositely disposed with respect to each other, as, for example, the recesses 31, 33.

The lead of the heater 20 nearest the cap 23 may be passed directly through the opening 41 to one of the binding-posts as, and the other lead of the heating element may be passed through an opening 42 in the end of the supporting tube, then through the tube, and through the opening 40 in the cap 23, and secured to the bindingpost 39.

If desired, the terminals from the heating unit may be secured under the screw-heads of the binding-posts, and terminals 43, 44 may be secured between pairs of nuts having threaded connection with the binding-posts.

From the foregoing description it will be apparent that a, separate recess is provided for each terminal of the heating element, and separate recesses are also provided for the external terminals. It will also be observed that each bindingpost and its two connecting terminals are separated from the other binding-post and its terminals by the intervening walls of insulating material 35, 3'7.

The combined length of the supporting tube 21, the cap 22, and the portion of the cap 23 which is confined within the guard tube 24 by the flange 28, may be slightly less than the length of the guard tube so as to provide for expansion should the supporting tube 21 increase in length to a greater extent than the guard tube 24 when the heater is raised to a high temperature.

In the construction of the device any appropriate materials may be used for the respective parts. Good results have been obtained by making the heating element of a nickel chromium alloy. The supporting tube 21 may be of Scotch glass or of ceramic material. The caps 22, 23

may be made of insulating material known as lava. The guard tube 24 and uniting elements 26, 27 may be of brass. The filling 25 should preterably comprise an inert powdered insulating material such as aluminum oxide or sand.

It will be observed that the various parts of the heater are all held in their assembled relations by four simple detachable connections, that is, in the form shown, the two threaded connections between the uniting elements 26, 27 and the guard tube 24, and the two threaded connections between the binding-posts 38, 39 and their nuts.

The device may be assembled by mounting the heating element on the support, placing the cap 22 over one end of the support, inserting these parts in the guard tube 24, applying the cap 26, filling the guard tube and tubular support with the powdered insulating material from the open end opposite the uniting element 26, threading the terminals 01. the heating element through the openings in the cap 23, inserting the cap in the guard tube and over the end of the supporting tube, applying the uniting element 27, and securing the electric terminals to the binding-posts. Should any irregularity develop during the operation of the heater calling for inspection, repairs or replacement of parts, the entire device may be very quickly and readily disassembled by disconnecting the heater terminals from the binding-posts, removing one o! the uniting elements, withdrawing the parts from the guard tube, and separating them. Any defective part may be repaired or replaced and the heater again quickly assembled.

If desired, the uniting elements may be slightly brazed at their margins in order to prevent accidental loosening or separation of the parts. When thus secured, the brazed portion may be filed away, after which the device may be disassembled and reassembled as already explained.

The invention is not intended to be limited to the specific form herein disclosed for purposes of illustration but should be regarded as covering modifications and variations thereof within the scope of the appended claim.

What is claimed is:

An electric heater comprising a support of insulating material, an electric heating element mounted on the support, a tubular guard surrounding the heating element and its support, a cap of insulating material inserted in the end of the guard and having a recess to receive the end of the support, a uniting ring by which the cap may be held in its assembled relation with respect to the guard and support, the cap having a central portion extended through and beyond the uniting ring and so formed as to provide four circumferentially-spaced recesses in its outer surface, separated by four intervening wall-like portions, binding-posts mounted in two or said walllike portions oppositely disposed with respect to each other, and spaced openings through said cap leading respectively from the interior of the heater to two of its recesses oppositely disposed with respect to each other, whereby the heater terminals may be passed through said openings and connected with external terminals by means of said binding-posts, a separate recess being provided for each oi. the four terminals, the respective pairs 01' terminals leading to the binding-posts mounted in two of the wall-like portions being separated from each other by the intervening wall-like portions of insulating material.

FRANK W. DEARBORN. 

